β分子筛的Si/Al比对PtZn催化丙烷非临氢脱氢性能的影响

Effect of Si/Al ratio of β zeolite on propane dehydrogenation without H2 over PtZn catalyst

  • 摘要: 采用共浸渍法制备PtZn/β-x(x为SiO2/Al2O3物质的量比)分子筛双金属催化剂,探究了β分子筛中硅铝比对丙烷非临氢脱氢反应性能的影响。采用XRD、BET、HAADF-STEM、NH3-TPD、C3H6-TPD等一系列表征技术对催化剂的物相结构、表面性质及其对丙烷非临氢脱氢反应性能的影响进行了研究。结果表明,催化稳定性随载体中Si/Al比的增大而提高(稳定性顺序:PtZn/DeAl-β > PtZn/β-40 > PtZn/β-30 > PtZn/β-25),而催化剂的强酸位点数量(PtZn/β-30 > PtZn/β-40 > PtZn/β-25 > PtZn/DeAl-β),在一定程度上受硅铝比的影响,与丙烯选择性顺序相反。因此,分子筛的Si/Al比对催化剂的性质有重要的调变作用,当催化剂强酸位点较少、丙烯吸附较弱、比表面积较大时,有助于提高丙烷转化率、丙烯选择性和催化稳定性。

     

    Abstract: In this study, the PtZn/β-x catalysts (x refers to SiO2/Al2O3 mole ratio) were synthesized by co-impregnation method and the effect of Si/Al ratio of the β zeolite on propane non-hydrogen dehydrogenation was explored. A series of characterization such as XRD, BET, HAADF-STEM, NH3-TPD, C3H6-TPD were applied to investigate the phase structure, surface properties of catalysts, and their effects on the reaction performances. The results showed that, with the increase of Si/Al ratio, the catalytic stability would be enhanced following the order of PtZn/DeAl-β > PtZn/β-40 > PtZn/β-30 > PtZn/β-25, while the number of strong acid sites of the catalyst (PtZn/β-30 > PtZn/β-40 > PtZn/β-25 > PtZn/DeAl-β) was affected by the Si/Al ratio to some extent, which was opposite to the order of the propylene selectivity. Therefore, the control of the Si/Al ratio of zeolite is very important for optimizing the properties of the catalysts for propane dehydrogenation reaction. The catalysts with few strong acid sites, weak adsorption of propylene and large specific surface area are contributed to higher propane conversion, propylene selectivity and catalytic stability.

     

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